Method for fabricating reticles for EUV lithography without the use of a patterned absorber

ABSTRACT

Absorber material used in conventional EUVL reticles is eliminated by introducing a direct modulation in the complex-valued reflectance of the multilayer. A spatially localized energy source such as a focused electron or ion beam directly writes a reticle pattern onto the reflective multilayer coating. Interdiffusion is activated within the film by an energy source that causes the multilayer period to contract in the exposed regions. The contraction is accurately determined by the energy dose. A controllable variation in the phase and amplitude of the reflected field in the reticle plane is produced by the spatial modulation of the multilayer period. This method for patterning an EUVL reticle has the advantages of (1) avoiding the process steps associated with depositing and patterning an absorber layer and (2) providing control of the phase and amplitude of the reflected field with high spatial resolution.

[0001] The United States Government has rights in this inventionpursuant to Contract No. W-7405-ENG-48 between the United StatesDepartment of Energy and the University of California for the operationof Lawrence Livermore National Laboratory.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to the production of reticles forextreme ultraviolet lithography, and more specifically, it relates tosystems and methods for directly writing patterns onto the reflectivemultilayer coating of an extreme ultraviolet lithography reticle.

[0004] 2. Description of Related Art

[0005] The standard reflective reticle blank for extreme ultravioletlithography (EUVL) consists of a thick substrate coated with areflective multilayer film. The reflective multilayer coating mayconsist of any of several different material combinations. The industrystandard is 40 layer pairs of molybdenum and silicon. Each layer pairhas a thickness of about 7 nm. To fabricate the EUVL reticle, abuffer-layer film of thickness 50-100 nm plus an absorber film ofthickness between 50 and 150 nm is deposited on the multilayerreflective coating and subsequently patterned. The buffer-layertypically consists of SiO₂, and is used to protect the multilayer duringpatterning and serves as a sacrificial layer for the repair of absorberdefects. Absorber materials such as Al, Cr or TiN produce a binarymodulation of the reflected field according to the spatial pattern togenerate the desired lithographic image. There are significant costs andissues associated with this process. For example, the buffer-layer filmneeds to be of sufficient thickness to protect the multilayer, but asthe (transparent) buffer-layer thickness increases the absorber isplaced higher above the multilayer surface. For extreme ultraviolet(EUV) light incident on the multilayer film at angles away from normalincidence, this results in reflected EUV light escaping from themultilayer where it typically would be caught by the absorber.

[0006] Reticles for EUV lithography other than the one discussed abovehave also been proposed. One design uses a patterned multilayer film,where the non-reflecting substrate effectively acts as the absorber.There are disadvantages with this approach, including the sharpness ofthe absorber edges that are produced. Another EUVL reticle proposal isto use a focused beam to pattern a multilayer-coated reticle bydestroying the reflectance of the multilayer in the areas that areexposed to the beam. The main disadvantage of this approach is thedifficulty in confining the affected region to a small area consideringthe significant damage that must be done to make the multilayernon-reflecting.

[0007] U.S. Pat. No. 5,521,031, titled “Pattern Delineating Apparatusfor use in the EUV spectrum” proposes a variant on the standard EUVLreticle. The patent incorporates the basic principles of an attenuatedphase shift reticle in a reflecting structure. This allows a smallamount of EUV light to be reflected from absorber layers, where the EUVlight is phase shifted by 180° relative to the reflective multilayer.This allows for an increase in the sharpness of the EUV light intensitymodulation at the wafer plane, and hence greater resolution.

[0008] It is desirable to eliminate the absorber material from an EUVLreticle by introducing a direct modulation in the complex-valuedreflectance of an EUVL reticle thin film multilayer.

SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to provide a method andapparatus for producing a direct modulation in the complex-valuedreflectance of the thin film multilayer of an EUVL reticle.

[0010] It is another object to provide a spatially localized energysource such as a focused electron or ion beam to directly writes areticle pattern onto the reflective multilayer coating.

[0011] Still another object of the invention is to directly write areticle pattern onto the reflective multilayer coating by activatinginterdiffusion within the film by an energy source that causes themultilayer period to contract in the exposed regions.

[0012] These and other objects will be apparent to those skilled in theart based on the disclosure herein.

[0013] The present invention eliminates the absorber material from anEUVL reticle by introducing a direct modulation in the complex-valuedreflectance of the multilayer. The reticle pattern is directly writtenonto the reflective multilayer coating with a spatially localized energysource such as a focused electron or ion beam. The energy sourceactivates interdiffusion within the film that causes the multilayerperiod to contract in the exposed regions. The contraction is accuratelydetermined by the energy dose. The spatial modulation of the multilayerperiod produces a controllable variation in the phase and amplitude ofthe reflected field in the reticle plane. This method for patterning anEUVL reticle has the advantages of (1) avoiding the process stepsassociated with depositing and patterning an absorber layer and (2)providing control of the phase and amplitude of the reflected field withhigh spatial resolution.

[0014] This invention has the potential to impact the extremeultraviolet lithography (EUVL) system currently under development atLawrence-Livermore National Laboratory (LLNL). In addition to strongcommercial applications (see below), EUVL has the potential to impactgovernment programs such as ASCII.

[0015] There is a strong commercial driving force for increasedminiaturization in electronic devices, and hence an extreme ultravioletlithography (EUVL) tool has significant commercial potential. For EUVLto be commercially viable the cost of ownership must be reasonable, andone of the more expensive components is the EUVL reticle. This inventionreduces the cost of EUVL reticles by eliminating the need for patternedabsorber layers on the multilayer-coated reticles

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1A shows a typical prior art reticle blank.

[0017]FIG. 1B shows a reticle blank after processing with a localizedenergy source.

[0018]FIG. 1C illustrates the effective resolution element.

[0019]FIG. 2 shows the results of a finite element simulation of thedeformation of a Mo/Si multilayer film produced.

[0020]FIG. 3 illustrates that the size of a depression at the multilayersurface can be controlled by controlling the exposure time.

[0021]FIG. 4 shows the temperature profile obtained for an electron beamof current I=3 μA and voltage V=10 kV.

[0022]FIG. 5 is a plot of the temperature as a function of radialposition on the top surface of the multilayer.

[0023]FIG. 6 shows the variation of temperature as a function of depth zat the center of the electron beam (r=0).

[0024]FIG. 7 shows a contour plot of the thickness of the silicideinterlayer after an electron beam exposure of 10 ms.

DETAILED DESCRIPTION OF THE INVENTION

[0025] This invention eliminates the need for an absorber material inreticles for extreme ultraviolet lithography (EUVL) by introducing adirect modulation in the complex-valued reflectance of the multilayer.The reticle pattern is directly written onto the reflective multilayercoating with a spatially localized energy source such as a focusedelectron or ion beam. FIG. 1A shows a typical prior art reticle blankconsisting of an A/B multilayer film 10 on a substrate 12, and FIG. 1Bshows a reticle blank after processing with a localized energy source,which is a focused beam in this example. The focused beam 14 activatesinterdiffusion within the film 16 that causes the multilayer period tocontract in the exposed regions. The contraction is accuratelydetermined by the energy dose. The spatial modulation of the multilayerperiod produces a controllable variation in the phase and amplitude ofthe reflected field in the reticle plane. In an A/B multilayer-coatedEUVL reticle blank, adjacent multilayer regions have the potential toreflect EUV light that will destructively interfere at the wafer planeif the EUV light reflected from a given region on the multilayer is 180°out of phase with the light reflected from adjacent regions on themultilayer. A 180° phase shift can be achieved by a suitable contractionof the multilayer. This contracted area coupled with adjacentuncontracted areas of the multilayer form the effective resolutionelement, since in the wafer plane, it will appear that there is no netEUV light reflected from this area of the reticle (due to destructiveinterference). This is the region that would be covered by an absorberfilm in a conventional reticle. The effective resolution element 18 isillustrated schematically in FIG. 1C.

[0026] The method described here for patterning an EUVL reticle has theadvantages of (i) eliminating the need to deposit and pattern anabsorber layer, (ii) providing control of the phase and amplitude of thereflected field, and (iii) eliminating the need for a buffer-layer,which can result in undesirable reflections. This reticle design alsoincorporates the primary benefit of an attenuated phase shift reticle inthat arbitrary control of the phase of the reflected light should allowfor an increase in the sharpness of the EUV light intensity modulationat the wafer plane, and hence greater resolution. This method also hasan advantage over the alternative reticle design in which focused beamsare used to selectively destroy the reflectivity of the multilayer tocreate a patterned reticle. The advantage is that in order to affect aminor contraction in the multilayer, much less energy has to bedeposited with the present invention. This should: (i) make it possibleto provide better spatial confinement of the beam, resulting in finerabsorber lines being possible and (ii) make for a faster patterningprocess.

[0027] In contracting the multilayer, there are two reasons why thephase will change relative to an adjacent, uncontracted region of themultilayer. The phase will change because (i) the height of themultilayer stack is decreased, and hence the EUV light will transverse alarger path relative to the uncontracted multilayer, and (ii) tocontract the multilayer stack there must be a small decrease in □ (onebi-layer period thickness) which will also result in a change in phase.To achieve a 180° phase shift, the contraction in the height of themultilayer stack will need to be approximately one bi-layer periodthickness, Λ. This is because the phase shift due to the decreasedbi-layer period is approximately one half of the phase shift due to thechange in the height of the multilayer stack, and is of the oppositesign (Reference: D. G. Stearns, R. S. Rosen and S. P. Vernon, in“Short-Wavelength Coherent Radiation: Generation and Applications”, Vol.11 of 1991 OSA Technical Digest Series (Optical Society of America,Washington, D.C., 1991), p. 152). For a typical Mo/Si multilayer-coatedreticle blank designed to reflect EUV light at 13.4 nm, this correspondsto a contraction of approximately 7 nm for the entire multilayer stackin the region of interest. Since the contraction can be shared amongmost, if not all of the bi-layers in the multilayer stack, Λ would needto contract by approximately 0.2 nm. This would translate to thewavelength of the reflectance peak being shifted by approximately 0.4 nmrelative to the uncontracted region, which is less than thefull-width-at-half-maximum (FWHM) of the Mo/Si reflectance peak, whichis typically 0.55 nm. This is important since if the difference in thewavelength of the reflected light from the contracted and uncontractedregions, Δλ, equals or exceeds the FWHM of the multilayer reflectancepeak, then the amplitude of the reflected field is reduced. Then bothphase and amplitude modulation can be achieved with this invention bycontrolling the amount of film contraction. The use of the materials ofMo/Si is presented as an example. Other multilayer combinations wouldwork equally well with the techniques presented herein. The equations,dosages, etc., would have to change and/or be optimized, but thetechnique for adjusting such for the different film pairs is asdisclosed.

[0028] It should also be noted that binary contrast (completely white orblack resolution elements) is usually not necessary or desirable.Therefore contractions in the multilayer stack of less than 7 nm areeffective, which may be advantageous since it requires smaller changesin Λ and hence lower Δλ.

[0029] In order to assess the viability of the present invention, finiteelement simulations were performed for the case of an electron beamimpinging on a localized area of a Mo/Si multilayer film. The localcontraction of the multilayer period due to silicide formation willproduce an indentation in the film in the vicinity of the electron beam.FIG. 2 shows the results of a finite element simulation of thedeformation 24 of a Mo/Si multilayer film 20 produced by a 10 msecexposure to an electron beam 22 of radius 25 nm, energy 10 kV, andcurrent 3 □A. The depression 24 at the surface is 12 nm, yet thecontraction of each multilayer period is only 0.5 nm. The size of thedepression at the surface can be controlled by controlling the exposuretime, as shown in FIG. 3. The lines at 30, 32 and 34 represent exposuretimes of 1 ms, 3 ms and 10 ms respectively. More information on thesesimulations is described below.

[0030] More specifically, finite element analysis was used to simulatethe temperature increase in a Mo/Si multilayer film due to the injectionof current by an electron beam. The Mo/Si multilayer film was modeled incylindrical coordinates (2D) as a disk of thickness 280 nm and radius 10μm on a Si substrate of thickness 1.12 μm. The multilayer film, whichactually is composed of 40 Mo/Si periods each having a thickness of 7.0nm, was treated as a single isotropic film for the purpose of the FEMmodeling. The material properties of the Mo/Si film and the Si substrateare listed in Table I. TABLE I Values for the thermal conductivity κ,the mass density ρ, the specific heat c_(p) and the conductivity σ usedin the FEM modeling. Material □(W/cm-° K) □(gm/cm³) c_(p) (J/gm-° K)σ(1/Ω-cm) Mo/Si ML 1.45 5.48 0.53 1 × 10⁴ Film Si substrate 1.49 2.330.71 1

[0031] The time-dependent temperature profile T(r,z;t) within themultilayer film was determined by solving the thermal diffusionequation: $\begin{matrix}{{{\frac{1}{r}\frac{\partial\quad}{\partial r}\left( {\kappa \frac{\partial T}{\partial r}} \right)} + {\frac{\partial\quad}{\partial z}\left( {\kappa \frac{\partial T}{\partial z}} \right)} - {\rho \quad c_{P}\frac{\partial T}{\partial t}} + {H\left( {r,{z;t}} \right)}} = 0} & (1)\end{matrix}$

[0032] Here H is the heat source. The electron beam voltage was chosento be sufficiently high (10 kV) so that the electron range wouldapproximately match the thickness of the multilayer film. Then it wasassumed that the energy was deposited uniformly through the film, withina cylinder of radius r₀=25 nm. (This oversimplified picture neglects thescattering of the electrons within the film, which could besignificant). In this model the heat deposited by the electron beam perunit volume was given by, $\begin{matrix}{H = \frac{IV}{\pi \quad r_{0}^{2}\tau}} & (2)\end{matrix}$

[0033] Here I and V are the respective current and voltage of theelectron beam and τ is the thickness of the multilayer film.

[0034] The time required for heat to diffuse a distance x is given byx²ρc_(p)/κ. Inserting the values from Table I, it is seen that heatdiffuses a micron in 20 ns. Hence, over the physical dimensions of thisproblem, the transient temperature dependence only lasts for tens ofnanoseconds. Since such short timescales are not of interest, Eq. (1)was simplified by dropping the dT/dt term and just solved for the steadystate temperature profile. The boundary conditions used in thecalculations were that the bottom and sides of the substrate and thesides of the multilayer film were maintained at a constant ambienttemperature of 300° K. The top surface of the multilayer film wasassumed to be thermally insulated (i.e., radiative cooling wasneglected).

[0035] The current density was adjusted to produce peak temperaturessufficiently high (>800° K) to activate the silicide formation thatcauses the contraction of the multilayer film. The temperature profileobtained for an electron beam of current I=3 μA and voltage V=10 kV isshown in FIG. 4. The temperature on the top surface is plotted in FIG. 5as a function of radial position. The variation of temperature as afunction of depth z at the center of the electron beam (r=0) is plottedin FIG. 6. It can be seen that the temperature has a maximum value of910° K at the top surface and decreases only to 880° K half way throughthe thickness of the film. Hence the heating is fairly uniform in depthdue to the penetration of the electron beam. FIG. 5 shows that thetemperature falls off rapidly in the radial direction, reducing to 700°K within 50 nm of the center of the electron beam.

[0036] Once the temperature profile is known, it is straightforward tocalculate the contraction of the multilayer film due to silicideformation. The reaction of Mo and Si at the interfaces is rate limitedby thermally activated interdiffusion (See “Silicide Layer Growth Ratesin Mo/Si Multilayers”, R. S. Rosen, D. G. Stearns, M. A. Viliardos, M.E. Kassner, S. P. Vernon and Y. Cheng, Appl. Optics 32, 6975 (1993),incorporated herein by reference.) The width of the interlayer increaseswith time according to:

w ² =w ₀ ²+2Dt  (3)

[0037] Here w₀=1.0 nm is the starting thickness of the interlayers inas-deposited films. The interdiffusion coefficient D is given by,

D=D ₀ exp(−E _(A) /kT)  (4)

[0038] Where D₀=50 cm²/s and E_(A)=2.4 eV for Mo/Si multilayer films.The formation of the silicide interlayer involves densification thatleads to a contraction of the multilayer period. The local change in theperiod is given by,

ΔΛ=Λ₀−α(w−w ₀)  (5)

[0039] Here α is the contraction factor that depends on the particularsilicide compound that is formed. In this study, α=0.38 is used, whichcorresponds to the contraction that occurs upon the formation of MoSi₂.

[0040] The growth of the silicide interlayer has an approximately squareroot dependence on the time that the film is subjected to heating, whichwill be referred to as the exposure time. Note that because the thermalresponse is so rapid, the transient heating and cooling times can beneglected. Contour plots showing the thickness of the silicideinterlayer after an exposure of 10 ms are presented in FIG. 7 for thecase of electron beam heating. The interlayer has a maximum thickness atthe surface of the film in the center of the current injection (r=0),and is approximately twice as thick as the as-deposited interlayer. Itis evident that the electron beam creates significant interlayer growthnearly half way through the entire thickness of the film. This is ofcourse due to the penetration of the electron beam, and the fairlyuniform heating through the thickness of the film. Because theinterlayer growth is in an activated process, it is only significant inthose regions reaching temperatures greater than ˜800° K.

[0041] The local contraction of the multilayer period produces anindentation in the film in the vicinity of the electron beam. Thestructural deformation in the Mo/Si multilayer film resulting from a 10ms exposure (I=3□A, V=10 kV) is shown in FIG. 2. Although the depressionat the surface is 12 nm deep, the contraction of each multilayer period,ΔΛ, is less than 0.5 nm. Consequently the primary effect of such adeformation on the EUV reflectivity of the multilayer film will be tocause a local phase perturbation. For larger deformations there willalso be a decrease in the reflectivity due to the decrease in contrastat the multilayer interfaces. Note also that the lateral width of thedeformation is contained within the region of the electron beam. Thedepth of the deformation is most easily controlled by adjusting theexposure time. Again, this is shown in FIG. 3, where the profile of thetop surface of the film is plotted for exposure times of 1, 3 and 10 ms.It is apparent that by adjusting the exposure time and the footprint,the detailed shape of the deformation and the corresponding phase shiftcan be accurately controlled.

[0042] These results show that an electron beam of moderate voltage (˜10kV) can be used to contract the period of a Mo/Si reflective coatingwithin a small spot defined basically by the footprint of the beam. (ForMo/Si, the key physical requirement on the energy deposition is thespatial resolution, i.e., small spot size, and energy sufficient toraise the temperature by hundreds of degrees. In the case of Mo/Si thisworks out to a deposited power in the range of 1-100 mW.) Thecontraction of the period, due to thermally activated silicide formationat the multilayer interfaces, occurs through approximately half thethickness of the film (20 periods). This produces a controllableindentation at the top surface having a depth that can exceed 10 nm.Since the film contraction generated by the electron beam is distributedover many periods, the primary effect of the deformation on the EUVreflectivity is a local phase shift of the reflected field.

[0043] The requirements of microamps of current at 10 kV are difficultto achieve within a spot size of ˜50 nm. One solution is to use fieldemission from a carbon nanotube. These nanotubes are tens of nanometersin diameter and are stable, high current field emitters capable ofdelivering microamps of current. (See A. G. Rinzler, J. H. Hafner, P.Nikolaev, L. Lou, S. G. Kim, D Tomanek, P. Nordlander, D. T. Colbert andR. E. Smalley, “Unraveling Nanotubes: Field Emission from an AtomicWire”, Science 269, 1550 (1995) incorporated herein by reference. Thenanotube could be integrated into the head of a scanning probemicroscope, and proximity focusing could be used to steer the extractedcurrent into a small spot on the surface of the film. The scanning probemicroscope can be used to locate and monitor the reticle fabricationprocess. Examples of carbon nanotubes are described in U.S. patentapplication Ser. No. ______, titled “A High-Current, High-Voltage, SmallDiameter Electron Beam Source Obtained By Field Emission From, And UsedIn Close Proximity To, A Single Carbon Nanotube” incorporated herein byreference.

[0044] The foregoing description of the invention has been presented forpurposes of illustration and description and is not intended to beexhaustive or to limit the invention to the precise form disclosed. Manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described to best explain theprinciples of the invention and its practical application to therebyenable others skilled in the art to best use the invention in variousembodiments and with various modifications suited to the particular usecontemplated. The scope of the invention is to be defined by thefollowing claims.

We claim:
 1. A method for fabricating reticles for use in an extremeultraviolet lithography (EUVL) system, comprising: providing an EUVLreticle that includes a substrate with a thin film multilayer coatinghaving a complex-valued reflectance; and changing the thickness of saidthin film multilayer coating to introduce a direct modulation in saidcomplex-valued reflectance.
 2. The method of claim 1, wherein said thinfilm multilayer coating comprises multiple layer boundaries, wherein thestep of changing the thickness of said thin film multilayer coatingincludes interdiffusing at least one layer boundary of said multiplelayer boundaries.
 3. The method of claim 1, wherein said thin filmmultilayer coating comprises a multilayer coating having multiple layerboundaries, wherein the step of changing the thickness of said coatingincludes altering the density of at least one layer of said thin filmmultilayer coating.
 4. The method of claim 1, wherein said thin filmmultilayer coating comprises multiple layer boundaries, wherein the stepof changing the thickness of said thin film multilayer coating includesinterdiffusing a plurality of layer boundaries of said multiple layerboundaries.
 5. The method of claim 2, wherein the step of interdiffusingat least one layer boundary includes controlling the multilayercontraction associated with the densification that occurs uponinterdiffusion at said at least one layer boundary.
 6. The method ofclaim 5, wherein the step of controlling the multilayer contractionincludes activating the step of interdiffusing using a localized energysource.
 7. The method of claim 6, wherein said localized energy sourcecomprises an electron beam.
 8. The method of claim 7, wherein saidelectron beam is focused.
 9. The method of claim 6, wherein saidlocalized energy source is selected from the group consisting of anelectromagnetic beam, an electron beam and an ion beam.
 10. The methodof claim 9, wherein said localized energy source is focused.
 11. Themethod of claim 6, wherein said localized energy source comprises anelectrode.
 12. The method of claim 1, wherein said thin film multilayercoating comprises Mo/Si.
 13. The method of claim 5, wherein saiddensification comprises silicide formation.
 14. The method of claim 9,further comprising controlling the change in thickness of said thin filmmultilayer coating by adjusting the energy dose of said localized energysource.
 15. The method of claim 9, further comprising adjusting theenergy dose of said localized energy source to control the change infilm thickness with sub-nanometer accuracy.
 16. The method of claim 9,further comprising controlling the lateral spatial resolution of thelocalization of energy deposition produced by said localized energysource.
 17. The method of claim 9, wherein the depth of the deformationis controlled by adjusting the exposure time of said localized energysource.
 18. An apparatus for fabricating reticles for use in an extremeultraviolet lithography (EUVL) system, comprising: means for positioningan EUVL reticle that includes a substrate with a thin film multilayercoating having a complex-valued reflectance; and means for changing thethickness of said thin film coating to introduce a direct modulation insaid complex-valued reflectance.
 19. The apparatus of claim 18, whereinsaid thin film multilayer coating comprises multiple layer boundaries,wherein said means for changing the thickness of said thin filmmultilayer coating comprises means for interdiffusing at least one layerboundary of said layer boundaries.
 20. The apparatus of claim 18,wherein said thin film multilayer coating comprises multiple layerboundaries, wherein said means for changing the thickness of said thinfilm multilayer coating comprises means for altering the density of atleast one layer of said multilayer coating.
 21. The apparatus of claim18, wherein said thin film multilayer coating comprises multiple layerboundaries, wherein said means for changing the thickness of said thinfilm multilayer coating includes means for interdiffusing a plurality ofsaid layer boundaries.
 22. The apparatus of claim 19, wherein said meansfor interdiffusing at least one layer boundary includes means forcontrolling the multilayer contraction associated with the densificationthat occurs upon interdiffusion at said at least one layer boundary. 23.The apparatus of claim 22, wherein said means for controlling themultilayer contraction comprises a localized energy source for producingenergy for activating said interdiffusion.
 24. The apparatus of claim23, wherein said localized energy source comprises an electron beamsource for producing said energy in the form of an electron beam. 25.The apparatus of claim 24, further comprising means for focusing saidelectron beam.
 26. The apparatus of claim 23, wherein said localizedenergy source is selected from the group consisting of anelectromagnetic beam source, an electron beam source and an ion beamsource.
 27. The apparatus of claim 26, further comprising means forfocusing said energy.
 28. The apparatus of claim 23, wherein saidlocalized energy source comprises an elect rode.
 29. The apparatus ofclaim 29, wherein said thin film multilayer coating comprises Mo/Si. 30.The apparatus of claim 26, further comprising means for adjusting theenergy dose of said localized energy source for controlling the decreasein thickness of said multilayer coating.
 31. The apparatus of claim 26,further comprising means for adjusting the energy dose of said localizedenergy source to control the decrease in film thickness withsub-nanometer accuracy.
 32. The apparatus of claim 26, furthercomprising means for controlling the lateral spatial resolution of thelocalization of energy deposition produced by said localized energysource.
 33. The apparatus of claim 30, further comprising means foradjusting the exposure time of said localized energy source forcontrolling the depth of the deformation.